Electrical driving means



g 1940- A. T. ROBERTSON 2,211,673

ELECTRICAL DRIVING MEANS Filed Aug. 12, 1938 5 Sheets-Sheet 1 l I B B g l f D l I I I. A5 A5 A5 11:" 0 c c c c D Fig.2;

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ELECTRICAL DRIVING MEANS Filed Aug. 12, 1938 5 Sheets Sheet 2 B) m, M WM ,4 TTOR/VE Y3 Aug. 13, 1940. A. T. ROBERTSON ELECTRICAL DRIVING MEANS Filed Aug. 12, 1938 5 Sheets-Sheet 3 R m w z N N 5 R v m HWMIWMIM 2 Aug. 13, 1940.

A. T. ROBERTSON 2,211,673 ELECTRICAL DRIVING MEANS Fiid Aug. 12, 1938 Fig. 8.

s Sheets-Sheet 4 mfmw /N VfNTOR BY M M WWW ATTORNEYJ ELECTRICAL DRIVING MEANS Filed Aug. 12, 1938 Fig. 9.

5 Sheets-Sheet 5 WM Mym Arro/e/vng Patented Aug. 13, 1940 H UNITED STATES 2,211,673 f 4 H ELECTRICAL DRIVING =MEAN S Alexander Thornton Robertson, Newcastle-on- Tyne, England, assignor, to J." H. Holmes & Company Limited, Hebburn on Tyne, England, a company of Great Britain Application August 12, 1938, Serial No. 224,612 In Great Britain August 17, 1937 This invention relates to electrical driving means for printing or other machines, or parts thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single speed, herein referred to as a crawling speed, substantially below the lowest normal speed. For example, in some cases acrawling speed as low as 5% of the lowest normal speed may be required. In the case of a printing press unit it is desirable that in normal operation the speed should be variable under the control of the operator over a comparatively wide range but that in addition it should be possible to run the press at an inching or crawling 151 speed considerably below the minimum speed ofthe normal range. Since speeds within the normal range are under the control of the operator, variation of speed due to gradual variation of the press torque is not objectionable. On the other hand, the inching or crawling speed is predetermined and not variable and it is therefore desirable that it should be as far as: possible constant and independent of the torque. g

An object of the invention is to provide driving means whereby the drive at normal and crawling speeds is effected by the same motor, the motor being an alternating current commutator motor which, for operation at normal speeds, is connected to a normal frequency supply and arranged'to function as a commutator motor, whilst for operation at crawling speed the motor is connected to a low frequency supply and arranged to'function as an induction motor.

'Thus, during normal operation the use of a communtator motor enables variation of speed to be effected at the will of the operator while maintaining electrical eificiency. On the other hand, at the crawling speed no substantial speed control is required and the use of the motor as an induction motor provides an arrangement in which the speed may vary but little with the torque.

In motors of the series type the stator windings usually constitute the primary windings and the rotor windings constitute the secondary windings, whilst in motors of the shunt type primary windings are-usually on the rotor and the secondary windings on the stator.

11A further object of the invention is to convert the motor, whether this is of the series type or shunt type, from commutator operation to induction operation by short-circuiting the secondary windings, for example by interconnecting the brushes. Alternatively in some cases it may be desirable to connect resistances across the,

13 Claims. (01. 172-230)" secondary windings in order to reduce the crawling, speed below that which would result if the secondary windings were directly short-circuited or to give an .increased torque when starting from restwith the motor operating as an induc- 5 tion motor. Such resistances may, if desired, be variable. In-the case of a motor of the shunt type the secondary windings will also require disconnection ;from the field windings whereas in the ,caseof a motor of series type, no change of 10 connections apart from the short-circuiting of the'secondary windings is required.

The invention may be carried into practice in various Ways but some practical arrangements according tozthe invention are shown diagram- 15 matically and by way of example in the accompanying drawings, in which- Figure, l shows one arrangement employing a motor of the series type,

Figure z-illustrates, on a larger scale, a modi- 20 fication of a part of the arrangement shown in Fi re. 1,:

- Figure 3,is another arrangement also employing a motor of-the series type,

Figure ishows a modification of a part of the 25 arrangement shown in Figure 3,

Figure, ,5, illustrates, in perspective, a device for short-circuiting the secondary or rotor windings and, disconnecting the brushes from the commutator, 30

.l1'Fig-ure 6: isgamodification of the arrangement shown in Figure 5,

-,-Figure ,7 shows one arrangement of the invention as applied to a motor of the shunt type,

Figures illustrates the invention as applied 35 to means ,for driving three units of a printing press, with mechanical synchronisation, and

Figure 9 is a modification of the arrangement shown in Figure 8, utilising electrical synchronisation. 40

In the arrangement shown in Figure 1 the motor, indicated-at A, is of the series type having stator or primary windings A and rotor or secondary windings A The motor windings A and A are respectively connected in series with 4.5 the ,primaryand secondary windings B B of a transformer B, the primary windings of which can be connected by a change-over switch C either throughcontacts C to normal frequency supply mains D- or through contacts C to low-frequency 50 supply mains D The brushes A through which the secondary windings A are fed are circumferentially-adiustable over the commutator A for the purpose of speed regulation under normal operating conditions, the leads A from the 55 brushes being connected to short-circuiting contacts C of the switch C.

Thus, during normal operation the switch C is set so as to connect the normal frequency mains D to the transformer B whilst the contacts C and C are open. The motor A now operates as a commutator motor and the operator can vary the motor speed over a wide range while maintaining electrical efficiency. On the other hand the motor can be run at a crawling speed considerably below the minimum speed of the normal range by setting the switch C in the position shown in the drawings whereby the primary motor windings A are connected through the contacts C to the low frequency supply mains D whilst the secondary motor windings A are short-circuited by closing of the contacts (3 and thus interconnecting the brushes A The motor A now operated as an induction motor whose speed may vary but little with variations in torque.

In some cases it may be desirable to connect resistances across the windings A of the motor A in qrder to reduce the crawing speed below that which would result if the windings were directly short-circuited as described with reference to Figure 1, or to give an increased torque when starting from rest with the motor operating as an induction motor. For example, as shown in Figure 2, a variable resistance E is provided in each of the leads A from the brushes A so that when the switch C is in the position shown the secondary windings A are short-circuited through the resistances E, each of which I can be adjusted to suit requirements.

In the modified arrangement shown in Figure 3, instead of directly shoit-circuiting the windings A the primary transformer windings B are. provided with short-circuiting switches B Thus, under normal conditions, the switches C and B are in the positions shown and the motor A operates as a commutator motor. For crawling speed, however, the switch C is operated to connect the transformer through the contacts C to the low-frequency supply mains D and the switches B are closed so as to shortcircuit the primary transformer windings B thus in effect short-circuiting the secondary motor windings A For the purpose described with reference to Figure 2, variable resistances E (Figure 4) may be provided in series with the switches B If desired short-circuiting of the secondary motor windings may be effected by means of contacts provided on the motor itself. One such arrangement is shown in Figure 5 in which three contacts F connected to the windings A are arranged within the commutator A and a sleeve F is mounted on a rod F so as to be longitudinally slidable thereon to and from the contacts F. A crank F secured to a control shaft F engages .a circumferential groove F in the sleeve F the shaft F also carrying a finger 1' which the sleeve F iA When, however, the motor speed rises the weight G causes the pawl G to move the sleeve F away from the contacts F, and at the same time returns the brushes A to the commutator A If desired the centrifugal device may be omitted and the sleeve F and brushes A? operated by turning the shaft F manually.

A modified arrangement for short-circuiting the secondary winding of the motor is shown in Figure 6 is which three contacts H are connected to the said secondary or rotor winding through the commutator A A short-circuiting disc H movable along a rod H is loaded by a spring H and, during operation of the motor on normal frequency, is held clear of the contacts H by an electromagnet H supplied through slip rings H from a source of supply H through a switch H". When the motor is to operate on the low-frequency supply the switch H is opened and the spring H moves the disc H so that the contacts H, and therefore the secondary windings of the motor, are short-circuited. A three-pole contactor H may also be provided with its operating coil in parallel with the electromagnet H so that when the switch H is opened the brushes A will be disconnected from the transformer secondary windings so as to prevent any circulation of current therein.

Figure 7 illustrates one arrangement of the invention as applied to a motor of the shunt type. In this arrangement the motor comprises primary windingsJ on the rotor and fed through slip rings J from leads J A commutator winding K, also on the rotor, is connected through brushes K to secondary windings L on the stator. For operation at speeds within the normal speed range a switch M connects the secondary windings L thrcugh'contacts M to the brushes K and at the same time connects the leads J through contacts -M to normal frequency supply mains N. The motor now operates as a normal shunt commutator motor and the operator can vary the speed as desired within the said speed range. For operation'at crawling speed the switch M is set in the position shown'inthe drawing, that is to say so that the brushes K are disconnected from the secondary be applied to the arrangement shown in Figure '7.

For example, a centrifugally or manually operatedshort-circuiting member, corresponding to the sleeve F in Figure 5, may cooperate with contacts, corresponding to the contacts M in Figure 7, for. short-circuiting the secondary windings, whilst the brushes K are simultaneously tilted away from the commutator in a manner similar to that described with reference to Figure 5. Alternatively, the-secondary windings L may be short-circuited by, an electromagnetically operated contact disc similar to that described with reference to Figure 6, with an associated threepole contactor (H in Figure 6) for disconnecting the secondary windings L from the brushes K When driving means according to the invention is employed for driving each of a number of units of a printing press, these units may be supply P maintained in synchronism either by mechanical or by electrical means.

One arrangement, embodying the invention, providing mechanical synchronism is shown diagrammatically and by way of example in Figure 8. In this arrangement three series mtors 0 each having primary and secondary windings supplied from a transformer P, as described with reference to Figure 1, drive three units of a printing press, namely two printing units Q and a folder Q The drive is transmitted from each motor 0 through a chain 0' toa synchronising shaft 0 from which the units Q and Q are driven through bevel gears 0 The primary windings of the transformers P are supplied from busbars P which can be connected at will by a contactor P either to normal frequency supply mains P or to low frequency supply mains P The contactor P comprises two coils P and P which can be connected by a switch P to the supply mains P Connected in parallel with the coil P are three further contactor coils R each of which controls contacts R for shortcircuiting the leads connecting the secondary windings of the corresponding transformer to the brushes of the associated motor 0. Speed control is effected by means of a pilot motor 0* which acts through a shaft 0 on the brush rockers of the three motors 0.

When operating at a speed within the normal speed range the switch P is in the position shown so that the coil P is energised and the busbars P and therefore the primary windings of the transformers P, are connected to the normal frequency supply mains P At the same time the coil P and therefore the coils R are deenergised so that the short-circuiting contacts R are open. The motors now operate as commutator motors and the speed can be varied by the operator within the normal range by means of the pilot motor 0 To operate at crawling speed the operator moves the switch P so as to energise the contactor coil P thus disconnecting the busbars from the normal frequency supply P and connecting them to the low frequency The contactor coils R are also energised so that the contacts R are closed to shortcircuit the secondary windings of the motors O. The motors now operate as induction motors at approximately constant crawling speed.

Figure 9 illustrates an arrangement similar to that described with reference to Figure 8 but employing electrical instead of mechanical synchronisation. Thus, in the arrangement shown in Figure 9, instead of employing a synchronising shaft interconnecting the bevel gears O as in Figure 8, three synchronising Selsyn machines S are employed, whilst speed control is effected by individual self-synchronising pilot motors T. Each of the Selsyn machines S is connected on the one hand through conductors S to the normal frequency supply mains P and on the other hand to a setof busbars S A relay U connected to the conductors S may be arranged with its contacts U in series with the switch P so as to prevent the motors 0 from being started unless the Selsyn machines S are correctly excited.

It will be understood that in Figure 8 self-synchronising pilot motors as shown at T in Figure 9 may be employed instead of the pilot motor 0 and shaft 0 Similarly in Figure 9 a single pilot motor and shaft may be employed instead of the individual self-synchronising motors T.

What I claim as my invention and desire to secure by Letters Patent is:

1. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor, primary and secondary windings on the motor, a source of current supply at normal frequency, a source of current supply at lower frequency, a switching device to connect said windings and sources for operation at normal speeds including contacts for connecting the primary winding of the motor to the normal frequency supply source, means associating the secondary winding with said source so that the motor operates as a commutator motor, and contacts on said switching device whereby the motor may be connected for operation at crawling speed, said second set of contacts being arranged to connect the primary winding of the motor to the lower frequency supply source and to short-circuit the secondary winding, the motor then operating as an induction motor.

2. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor, primary and secondary windings on the motor, a transformer having primary and secondary windings respectively connected in series with the primary and secondary windings of the motor, a source of current supply at normal frequency, a source of current supply at lower frequency, a switching de vice having contacts whereby, for operation at normal speeds, the primary windings of the trans-a former are connected to the normal frequency supply source and both the primary and secondary windings are energized so that the motor operates as a commutator motor, and other contacts whereby, for operation at crawling speed, the primary windings of the transformer are connected to the lower frequency supply source and the secondary windings of the transformer are effectively short-circuited, so that the primary winding of the motor is energized whereas the secondary motor winding is de-energized, the motor then operating as an induction motor.

3. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor, primary and secondary windings on the motor, a transformer having primary and secondary windings respectively connected in series with the primary and secondary windings of the motor, at least one shortcircuiting resistance for the secondary windings of the transformer, a source of current supply at normal frequency, a source of current supply at,

lower frequency, a switch device having contacts whereby, for operation at normal speeds, the primary windings of the transformer are connected to the normal frequency supply source so that both the primary and secondary windings of the motor are energized and the motor operates as n a commutator motor, and other contacts whereby, for operation at crawling speed, the primary windings of the transformer are connected to the lower frequency supply source and the secondary windings of the transformer are short-circuited through the said resistance, the primary motor win'dingbeing thus energized whereas the.secondary winding of the motor is de-energized and the motor operates as an inductionimotor.

14. In electrical driving means for a printing or other machine, or part thereof, requiring to be drivenat a speed adjustable throughout a substantial range of normal speeds and also at a single crawling'speed substantially below the.

lowest normal speed, in combination, an alternating current commutator motor of the series type comprising a primary stator winding, a secondaryrotor winding, and a commutator connected to the secondary. winding, brushes bearing on the commutator, a device for short-circuiting the brushes, a source of current supply at normal frequency, a source of. current. supply at lower frequency, a device having contacts whereby, for operation at normal speeds, the primary winding of the motor is connected to the normal frequency supply. source and thesecondary motor winding is energized so that the motor operates as a commutator motor, and other contacts whereby, for operation at crawling speed, the primary winding of the motor is connected to the lower frequency supply source, the brushes being short-circuited by the said short-circuiting device, so that the primary winding is energized and the secondary winding is de-energized, the motor then operating as an induction motor.

i 5. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor, primary and secondary windings on the motor, brushes connected to the secondary winding, contacts connected to the secondary winding, a short-'circuiting device cooperating with the said contacts, means for disconnecting the brushes from the secondary winding, means automatically actuated in accordance with the speed of the motor for causing relative movement of the said device and the cooperating contacts and simultaneously disconnecting the brushes from the secondary winding, a source of current supply at'normal frequency, a source of current supply at lower frequency, a device having contacts whereby, for operation at normal speeds, the primary winding of the motor is connected to the normal frequency supply source and the secondary winding is energized so that the motor operates as a commutator motor,

1 and other contacts whereby, for operation at crawling speed the primary winding of the motoris connected to the lower frequency supply source,

the short-circuiting device being moved upon op-' eration of said device into engagement with the cooperating contacts thereby short-circuiting the secondary winding and disconnecting the brushes therefrom so that the primary winding of the of current supply at lower frequency, a changeover switch which, in one position, connects the primary winding of the motor to the normal frequency supply sourceand causes energization of the secondary winding so that the motor operates as .a commutator motor for operation at normal speeds, the said switch, when in another position, connecting the primary winding of the motor to the lower frequency supply source and effectively short-circuiting the secondary winding through the said resistance so that the primary winding is energized but the secondary winding is deenergized, the motor then operating as an induction motor.

, '7. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor having primary and secondary windings, a source of current supply at normal "frequency, a source of current supply at lower frequency, a change-over switch having cooperating contact sets, which, in one position, connect the primary winding of the motor to the normal frequency supply source and simultaneously energize the secondary winding so that the motor operates as a commutator motor for normalspeeds, and in another position connect the said primary winding to the lower frequency supply source and short circuits the secondary windings so that the motor operates as an induction motor for crawling speeds.

8. In electrical driving means for a printing or othermachine, or part thereof, requiring to be driven at aspe'ed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor having primary and secondary windings, at least one short-circuiting resistance for the secondary winding, a source of current supply at normal frequency, a source of current supply at lower frequency, a switch device'for connecting the primary winding to the normal frequency supply source, a switch device for connecting the primary winding'to the lower frequency supply source, and a switch device for efiectively short-circuiting the secondary winding through said resistance, so that for operation at normal speeds the primary winding is connected to the normal frequency supply source and the secondary winding is energized and the motor operates as a commutator motor, whereas for operation at crawling speed the primary winding is connected to the lower frequency supply source and the secondary winding is effectively short-circuited through the said resistance and the motor operates as an induction motor.

9. Electrical driving means as claimed in claim 8, in which the effective value of the short-circuiting resistance is variable.

10. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor, primary and secondary windings on the motor, a transformer having primary and secondary windings respectively connected in series With the primary and secondary windings of the motor, a source of ourrent supply at normal frequency, a source of cur rent supply at lower frequency, a change-over switch which, in one position, connects the primary windings of the transformer to the normal frequency supply source thus energizing both the primary and secondary motor windings so that the motor operates as a commutator motor within the normal speed range, and in another position connects the primary windings of the transformer to the lower frequency supply source and effectively short-circuits the secondary transformer windings so that the primary motor winding is energized whereas the secondary motor winding is tie-energized and the motor operates as an induction motor at crawling speed.

11. in electrical driving means the combination with the features claimed in claim ll), of at least one variable resistance through which the secondary windings of the transformer are shortcircuited.

12. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor of the series type comprising a primary stator winding, a secondary rotor winding, a commutator connected to the secondary winding, brushes bearing on the commutator, a source of current supply at normal frequency, a source of current supply at lower frequency, and a change-over switch which, in one position, connects the primary winding of the motor to the normal frequency supply source thus causing the secondary winding to be energized so that the motor operates as a commutator motor within the normal speed range, and in another position connects the primary winding of the motor to the lower frequency supply source short-circuits the brushes thus de-energizing the secondary winding of the motor then operating as an induction motor at crawling speed.

13. In electrical driving means for a printing or other machine, or part thereof, requiring to be driven at a speed adjustable throughout a substantial range of normal speeds and also at a single crawling speed substantially below the lowest normal speed, in combination, an alternating current commutator motor comprising a primary or stator winding and a secondary or rotor winding, a source of current supply at normal frequency, a source of current supply at lower frequency, switching means to connect said windings and sources for operation at normal speeds including contacts for connecting the primary winding of the motor to the normal frequency supply source, means associating the secondary winding with said source so that the motor operates as a commutator motor, a second set of contacts included in said switching means whereby the motor may be connected for operation at crawling speed, said second set of contacts being arranged to connect the primary winding of the motor to the lower frequency supply source and a third set of contacts included in said switching means whereby the secondary winding can be short-circuited when the second set of contacts connects the primary winding to the lower frequency supply source, the motor then operating as an induction motor.

ALEXANDER THORNTON ROBERTSON. 

